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Huge barrel jellyfish filmed off Cornwall coast

30 June 2014 Last updated at 13:29 BST

A giant barrel jellyfish has been spotted swimming in an estuary in Cornwall.

Matt Slater of the Cornwall Wildlife Trust swam around the jellyfish to capture this video - which also shows his dog paddling nearby!

The jellyfish is said to weigh as much as 20kg and measure around a metre across.